Spontaneous nontraumatic hemoperitoneum due to a bleeding arteriovenous malformation on the serosal surface of the transverse colon: a case report.

Arteriovenous malformations of the gastrointestinal tract are a very common entity and a frequently cited cause of lower gastrointestinal bleeding in adults. They are characteristically found in the mucosa or submucosa of the bowel wall, and the vast majority do not cause any symptoms. We discuss the rare case of an extraluminal arteriovenous malformation of the transverse colon in an elderly woman who presented to the emergency department in hypovolemic shock after collapsing at home. An exploratory laparotomy was performed after a diagnostic peritoneal lavage yielded gross blood. The patient was found to have a spontaneously bleeding lesion confined to the serosal surface of the right transverse colon, which histological examination revealed to be an arteriovenous malformation. The lesion was excised and the patient recovered without sequelae. To date there have been no other documented cases of an arteriovenous malformation on the serosal surface of a visceral abdominal organ.